So now we have all the information to start or not ? Often new sources come available during the proces which makes the proces easier but sometimes it means also a complete new start.

If only pictures are available I have to make an estimate of the sizes by comparing the part to surrounding things from which I have some dimensions. I have to compensate for perspective and camera distortions.

Then the real work starts. I begin making a sketch on a flat plane ( like a normal drawing ). After this I give thickness/body to the object. Then I construct the holes as postive material and subtract them from the first object. Sometimes it's like you would normally make the part: you start with a big piece of material and by removing material you shape the part. See below for an animation of the creation of the virtual object.

STEP 3 : THE DRAWING